1. Field of the Invention
The present invention relates to an armature winding for a dynamo-electric machine such as a two-pole, three-phase turbine generator. The present invention relates to, in particular, an armature winding for a dynamo-electric machine having three parallel connected circuits for each phase.
2. Description of the Prior Art
Normally, an armature winding in a high-capacity turbine generator includes upper coil pieces and lower coil pieces accommodated in upper and lower portions of the slots of a layered core, respectively. The upper coil pieces and the lower coil pieces are connected in series thereby increasing voltage generated at the pieces and the capacity of the generator. When the voltage of the armature winding increases, however, the thickness of the main insulating member of the armature winding increases, with the result that the cross-sectional area of a conductor portion of the armature winding decreases and current density increases so as to cause the increase of loss.
In addition, in an indirect cooling type machine for cooling an armature winding from the outside of the main insulating member of the armature winding, there is the possibility that the thickness of the main insulating member induces an increase in heat resistance of the armature winding, thereby disadvantageously increasing the temperature of the armature winding.
To avoid this disadvantage, while the capacity of a generator is kept unchanged, an armature winding is divided into a plurality of parallel connected circuits so as to decrease generated voltage, thereby decreasing loss and improving cooling capability. In a high capacity generator of indirect cooling type, in particular, it is ordinarily seen that the number of slots increases to increase the cooling circumference. It is, therefore, necessary to provide an armature winding having parallel connected circuits more than three parallel connected circuits.
When an armature winding having more parallel connected circuits than three parallel connected circuits is applied to a two-pole dynamo-electric machine, it is impossible to make the voltage generated at the respective parallel connected circuits completely the same. As a result, circulating current occurs between the parallel connected circuits so that the loss of the armature winding disadvantageously increases. To decrease the circulating current loss, it is essential to reduce the voltage unbalance between the parallel connected circuits as much as possible. To reduce the voltage unbalance between the circuits, it is necessary to specially arrange coils belonging to the respective parallel connected circuits in the respective phase belts.
For example, as disclosed in U.S. Pat. No. 2,778,963 to Rudolf Haberman issued on Jan. 22, 1957, it is necessary to arrange coils of the respective parallel circuits in the respective belts so as to minimize the deviation between the absolute values of the voltages generated at the respective parallel connected circuits and the deviation between phase angles of the respective parallel connected circuits so as to reduce voltage unbalance between the respective parallel connected circuits.
An armature winding of a two-pole, three-phase dynamo-electric machine normally has two phase belts per phase. Thus, by mutually connecting these two phase belts to cancel their counterpart voltage unbalance, voltage unbalance is reduced. However, when the number of slots is odd, the number of coils of the two phase belts do not coincide with each other, in a case of using the above-stated method, it is difficult to reduce voltage unbalance between the circuits. As an example of a method of reducing voltage unbalance in a case where the number of slots is odd, there is disclosed a dynamo-electric machine having 45 slots in U.S. Pat. No. 3,652,888 to Dean Harrington issued on Mar. 28, 1972. According to Harrington, the deviation of phase angles among the three parallel connected circuits is 0.13xc2x0 to 0.14xc2x0 . Judging from the standard set by Haberman that the deviation between phase angles is 0.15xc2x0 or less, it is hard for Harrington to maintain sufficient voltage balance between circuits.
Furthermore, owing to reduce the voltage unbalance, the mechanical structure of the armature winding of Harrington is disadvantageously slightly complicated.
This is because, due to the irregular arrangement of coils belonging to the respective parallel connected circuits in each phase belt, it is necessary to provide a lot of jumper wires for connecting upper and lower coil pieces at each coil end.
To avoid interference between the respective jumper wires, and interference between the respective jumper wires and the connecting portions of the usual respective upper and lower coil pieces to the lead wires, excessive space is required in the dynamo-electric machine so that the length of the dynamo-electric machine increases. In addition, the workload required to connect the large number of jumper wires increases. Furthermore, since each of the jumper wires is longer than the usual upper and lower coil connection pieces, there is the possibility that reliability of the connection portions of the jumper wires and the lead wires is decreased.
The present invention is directed to overcome the foregoing problems.
Accordingly, it is an object of the present invention to provide a three phase armature winding of a dynamo-electric machine having three parallel connected circuits per phase, wherein two (first and second) phase belts of each phase are arranged in two (first and second) slot groups each having slots and a number of slots of the first slot group is different from a number of slots of the second slot group, which is capable of reducing the number of jumper wires at coil ends and reducing voltage unbalance between parallel connected circuits.
In order to achieve such object, according to one aspect of the present invention, there is provided a three phase armature winding for a dynamo-electric machine, in which the three phase armature winding is disposed in a core, the core having a number of slots, each phase of the armature winding comprising: a first phase belt for a first slot group having (3n+2) slots; a second phase belt for a second slot group having (3n+1) slots; three parallel connected circuits each constituting a number of series connected coils per circuit, each of the series connected coils per circuit having a first coil piece and a second coil piece connected thereto in series, each of the first coil piece and the second coil piece having one end portion and other end portion, the first phase belt housing (3n+2) series connected coils of the parallel connected circuits and the second phase belt housing (3n+1) series connected coils thereof, when the three parallel connected circuits in each phase are designated circuit numbers, respectively, the three parallel connected circuits in each phase being arranged so that a circuit sequence of the circuit numbers of the first coil pieces in each of the first and second phase belts and a circuit sequence of the circuit numbers of the second coil pieces therein are substantially the same; and a pair of connection members mounted at the other end portion side of the series connected coils in the first phase belt whereby part of the first coil pieces in the first phase belt and part of the second coil pieces therein are connected so that the circuit sequence of the part of the first coil pieces is interchanged with that of the part of the second coil pieces.
In preferred embodiment of this aspect, the three phase armature winding is composed of a two layer lap winding, each of the connection members is a jumper wire and the slots are arranged in sequence about a rotor of the core.
In preferred embodiment of this aspect, an arrangement position of each of the jumper wires is determined so that a voltage unbalance among the three parallel connected circuits is reduced and a phase of a highest voltage in voltages induced in the respective parallel connected circuits is lagging with respect to a phase of an average voltage of a whole phase.
In preferred embodiment of this aspect, the first slot group has 11 slots, the second slot group has 10 slots, the first phase belt houses 11 series connected coils, the second phase belt houses 10 series connected coils, when the circuit numbers of the three parallel connected circuits are 1, 2, 3, the circuit sequences of the first and second coil pieces of the parallel connected circuits in the second phase belt are 1, 2, 3, 1, 2, 3, 1, 2, 3, 1 from a beginning of the first coil pieces in the first phase belt toward an end of the second coil pieces in the second phase belt, the circuit sequence of the first coil pieces of the parallel connected circuits in the first phase belt is 2, 3, 1, 3, 2, 1, 3, 2, 1, 3, 2 from the beginning side toward the end side, and wherein the circuit sequence of the second coil pieces of the parallel connected circuits in the first phase belt is 3, 2, 1, 3, 2, 1, 3, 2, 1, 3, 2 from the beginning side toward the end side.
In preferred embodiment of this aspect, the first slot group has 8 slots, the second slot group has 7 slots, the first phase belt houses 8 series connected coils, the second phase belt houses 7 series connected coils, when the circuit numbers of the three parallel connected circuits are 1, 2, 3, the circuit sequence of the first coil pieces of the parallel connected circuits in the first phase belt is 2, 3, 1, 3, 2, 1, 3, 2 from a beginning of the first coil pieces in the first phase belt toward an end of the second coil pieces in the second phase belt, the circuit sequence of the second coil pieces of the parallel connected circuits in the first phase belt is 3, 2, 1, 3, 2, 1, 3, 2 from the beginning side toward the end side, and wherein the circuit sequences of the first and second coil pieces of the parallel connected circuits in the second phase belt are 1, 2, 3, 1, 2, 3, 1 from the beginning side toward the end side.
According to the aspect of the present invention, at the other end in the first phase belt corresponding to the (3n +2) slots, the pair of connection members, such as the pair of jumper wires is provided whereby part of the circuit sequence of the first coil pieces in the first phase belt is changed from part of the circuit sequence of the second coil pieces therein so that the voltage generated at the first coil pieces becomes substantially equal to that generated at the second coil pieces and the number of the remaining first and second coil pieces in the first phase belt becomes apparently substantially equal to that of the first and second coil pieces in the second phase belt. Thus, it is possible to improve the balance of voltages generated at the parallel connected circuits.
Further, in this aspect of the present invention, since only one pair of two jumper wires is provided at the other end portion side of the coils in the first phase belt per phase, it is possible to simplify the structure of the coil end portion so as to shorten the jumper wires and to finally improve reliability for the connection of the coil end portion.
According to this aspect of the present invention, the arrangement positions of the jumper wires are determined so that the unbalance of voltages generated at the three parallel connected circuits is reduced and the highest voltage among those generated at the respective circuits is lagging in phase with respect to the average voltage of the three parallel connected circuits. The circulating current generated due to voltage unbalance among the three parallel connected circuits is lagging in phase by about 90 degrees with respect to the unbalanced voltage so that the voltage which is lagging in phase with respect to the average voltage of the three parallel connected circuits causes circulating current opposite in phase to the armature current which is substantially equal in phase to the average voltage. It is, therefore, possible to suppress the increase of armature current resulting from the circulating current and to suppress the increase of loss resulting from the circulating current.
In accordance with this aspect of the present invention, since a structure of this aspect of the present invention is applied to an armature winding having a first phase belt for 11 slots and a second phase belt for 10 slots, it is possible to provide the same function and advantage described above.
In accordance with this aspect of the present invention, since a structure of this aspect of the present invention is applied to an armature winding having a first phase belt for 8 slots and a second phase belt for 7 slots, it is possible to provide the same function and advantage described above.
In order to achieve such object, according to another aspect of the present invention, there is provided a three phase armature winding for a dynamo-electric machine, in which the three phase armature winding is disposed in a core, the core having a number of slots, each phase of the armature winding comprising: a first phase belt for a first slot group having (6nxc2x12) slots; a second phase belt for a second slot group having (6nxc2x11) slots; three parallel connected circuits each constituting a number of series connected coils per circuit, each of the series connected coils per circuit having a first coil piece and a second coil piece connected thereto in series, each of the first coil piece and the second coil piece having one end portion and other end portion, the first phase belt housing (6nxc2x12) series connected coils of the parallel connected circuits and the second phase belt housing (6nxc2x11) series connected coils thereof, when the three parallel connected circuits in each phase are designated circuit numbers, respectively, the three parallel connected circuits in each phase being arranged so that a circuit sequence of the circuit numbers of the first coil pieces in each of the first and second phase belts and a circuit sequence of the circuit numbers of the second coil pieces therein are substantially the same; a first pair of connection members mounted at the other end portion side of the series connected coils in the first phase belt whereby part of the first coil pieces in the first phase belt and part of the second coil pieces therein are connected so that the circuit sequence of the part of the first coil pieces is interchanged with that of the part of the second coil pieces; and a second pair of connection members mounted at the one end portion side of the series connected coils in the second phase belt whereby part of the first coil pieces in the second phase belt and part of the second coil pieces therein are connected so that the circuit sequence of the part of the first coil pieces is interchanged with that of the part of the second coil pieces.
In preferred embodiment of this another aspect, the first slot group has 10 slots, the second slot group has 11 slots, the first phase belt houses 10 series connected coils, the second phase belt houses 11 series connected coils, when the circuit numbers of the three parallel connected circuits are 1, 2, 3, the circuit sequence of the first coil pieces of the parallel connected circuits in the first phase belt is 1, 2, 3, 1, 2, 3, 1, 3, 2, 1 from a beginning of the first coil pieces in the first phase belt toward an end of the second coil pieces in the second phase belt, the circuit sequence of the second coil pieces of the parallel connected circuits in the first phase belt is 1, 2, 3, 1, 3, 2, 1, 3, 2, 1 from the beginning side toward the end side, and wherein the circuit sequences of the first and second coil pieces of the parallel connected circuits in the second phase belt are 3, 2, 1, 3, 2, 1, 2, 3, 1, 2, 3 from the beginning side toward the end side.
In preferred embodiment of this another aspect, the first slot group has 8 slots, the second slot group has 7 slots, the first phase belt houses 8 series connected coils, the second phase belt houses 7 series connected coils, when the circuit numbers of the three parallel connected circuits are 1, 2, 3, the circuit sequence of the first coil pieces of the parallel connected circuits in the first phase belt is 2, 3, 1, 2, 3, 1, 3, 2 from a beginning of the first coil pieces in the first phase belt toward an end of the second coil pieces in the second phase belt, the circuit sequence of the second coil pieces of the parallel connected circuits in the first phase belt is 2, 3, 1, 3, 2, 1, 3, 2 from the beginning side toward the end side, and wherein the circuit sequences of the first and second coil pieces of the parallel connected circuits in the second phase belt are 1, 3, 2, 1, 2, 3, 1 from the beginning side toward the end side.
According to this another aspect of the present invention, a pair of connection members, such as, jumper wires connect the first coil pieces and the second coil pieces in the first phase belt whereby part of the circuit sequence of the first coil pieces in the first phase belt is changed from part of the circuit sequence of the second coil pieces therein. In addition, another pair of connection members, such as jumper wires connect the first coil pieces and the second coil pieces in the second phase belt whereby part of the circuit sequence of the first coil pieces in the second phase belt is changed from part of the circuit sequence of the second coil pieces therein.
As a result, since the arrangement of circuit sequences indicating the arrangement of the parallel connected circuits are symmetrical about the center of each phase belt, the phase angles of the voltages generated at the respective parallel connected circuits substantially coincide with each other, thereby making it possible to reduce voltage unbalance among the parallel connected circuits.
Further, in this another aspect of the present invention, since each of pairs jumper wires is provided at each of the one end side and the other end side of the coils, it is possible to simplify the structures of the both coil end portions so as to shorten the jumper wires and to finally improve reliability for the connection of the coil end portions.
In accordance with this another aspect of the present invention, since a structure of this another aspect of the present invention is applied to an armature winding having a first phase belt for 10 slots and a second phase belt for 11 slots, it is possible to provide the same function and advantage described above.
In accordance with this another aspect of the present invention, since a structure of this another aspect of the present invention is applied to an armature winding having a first phase belt for 8 slots and a second phase belt for 7 slots, it is possible to provide the same function and advantage described above.
In order to achieve such object, according to further aspect of the present invention, there is provided a three phase armature winding for a dynamo-electric machine, in which the three phase armature winding is disposed in a core, the core having a number of slots, each phase of the armature winding comprising: a first phase belt for a first slot group having (6nxc2x12) slots; a second phase belt for a second slot group having (6nxc2x11) slots; three parallel connected circuits each constituting a number of series connected coils per circuit, each of the series connected coils per circuit having a first coil piece and a second coil piece connected thereto in series, each of the first coil piece and the second coil piece having one end portion and other end portion, the first phase belt housing (6nxc2x12) series connected coils of the parallel connected circuits and the second phase belt housing (6nxc2x11) series connected coils thereof, when the three parallel connected circuits in each phase are designated circuit numbers, respectively, the three parallel connected circuits in each phase being arranged so that a circuit sequence of the circuit numbers of the first coil pieces in each of the first and second phase belts and a circuit sequence of the circuit numbers of the second coil pieces therein are substantially the same; a first pair of connection members mounted at the other end portion side of the series connected coils in the first phase belt whereby part of the first coil pieces in the first phase belt and part of the second coil pieces therein are connected so that the circuit sequence of the part of the first coil pieces is interchanged with that of the part of the second coil pieces; and second two pairs of connection members mounted at the other end portion side of the series connected coils in the second phase belt whereby two pairs of the first coil pieces and the second coil pieces in the second phase belt are connected so that the circuit sequence of the paired first coil pieces is interchanged with that of the paired second coil pieces.
In preferred embodiment of this further aspect, the first slot group has 10 slots, the second slot group has 11 slots, the first phase belt houses 10 series connected coils, the second phase belt houses 11 series connected coils, when the circuit numbers of the three parallel connected circuits are 1, 2, 3, the circuit sequence of the first coil pieces of the parallel connected circuits in the first phase belt is 1, 2, 3, 1, 2, 3, 1, 3, 2, 1 from a beginning of the first coil pieces in the first phase belt toward an end of the second coil pieces in the second phase belt, the circuit sequence of the second coil pieces of the parallel connected circuits in the first phase belt is 1, 2, 3, 1, 3, 2, 1, 3, 2, 1 from the beginning side toward the end side, the circuit sequence of the first coil pieces of the parallel connected circuits in the second phase belt is 3, 2, 1, 3, 2, 1, 2, 3, 1, 2, 3 from the beginning side toward the end side, and wherein the circuit sequence of the second coil pieces of the parallel connected circuits in the second phase belt is 3, 2, 1, 2, 3, 1, 2, 3, 1, 3, 2 from the beginning side toward the end side.
According to the further aspect of the present invention, a pair of connection members, such as, jumper wires connect the first coil pieces and the second coil pieces in the first phase belt whereby part of the circuit sequence of the first coil pieces in the first phase belt is changed from part of the circuit sequence of the second coil pieces therein. In addition, another two pairs of connection members, such as two pairs of jumper wires connect the first coil pieces and the second coil pieces whereby two parts of the circuit sequence of the first coil pieces in the second phase belt are changed from two parts of the circuit sequence of the second coil pieces therein, respectively. As a result, the arrangement of circuit sequences indicating the arrangement of the parallel connected circuits is symmetrical about the center of each phase belt. Therefore, the phase angles of the voltages generated at the respective parallel connected circuits substantially coincide with each other, thereby making it possible to reduce voltage unbalance among the parallel connected circuits.